To allow a plurality of users to look at the same display screen, there is a method of connecting a video output of a PC (Personal Computer) to a video input of a projector, and projecting the display screen of the PC by the projector. A projector has been mainly used for projecting the display screen of one PC. In recent years, however, a projector is also used for projecting the display screen of one of PCs brought by a plurality of users while switching the PCs during the progress of a conference. When displaying the screen of one of a plurality of PCs while switching the PCs, the following method is adopted. That is, a video output of each PC is connected to a video input of a switching unit having a plurality of inputs, and a PC whose screen is to be projected by a projector is selected by operating a switch of the switching unit. In this case, it is cumbersome to move to a place where the switching unit is, and then operate it. Japanese Patent Laid-Open No. 2002-108321 has disclosed a technique with which the operator of a PC can switch the switching unit at hand. Japanese Patent Laid-Open No. 2006-23551 has disclosed a projector incorporating a switching function.
Furthermore, a projector can display an image of an image capturing apparatus such as a digital camera in place of the display screen of a PC. When displaying an image of a digital camera, the digital camera is connected to a projector via a cable such as a USB or LAN cable, and transmits an image file to the projector. The projector decodes and displays the transmitted image file.
Conventionally, however, when switching a video projected by a projector between the display screen of a PC and an image of a digital camera, a switching operation is necessary.